1. Technical Field
The present invention relates to a recording apparatus provided with a power transmission mechanism for driving a feeding roller and a one-way compound gear mechanism.
In the application, the recording apparatus includes an ink jet printer, a copying machine, a facsimile or the like.
2. Related Art
In recent years, a recording apparatus has a configuration in which a feeding roller is driven by a driving force of a transporting roller. Furthermore, in such a recording apparatus, a reversal passage to reverse a recording medium is provided for performing a double-sided recording. Therefore, in the recording apparatus, one recording surface of the recording medium is recorded by a recording portion, and then the recording medium is sent to the reversal passage by rotating the transporting roller reversely. Subsequently, the recording medium is resent to a feeding passage by the feeding roller, and the other recording surface is recorded by the recording portion. Thereafter, the recording medium is discharged from the recording apparatus.
However, it is necessary for the recording apparatus to cause the feeding roller to rotate in the same direction regardless of a forward rotation or a reverse rotation of the transporting roller. Therefore, a recording apparatus of which a driving mechanism for driving a feeding roller is provided with a one-way clutch has been disclosed in JP-A-10-331941.
The one-way clutch disclosed in JP-A-10-331941 includes a planetary gear, an inner member provided with a recessed portion for accommodating the planetary gear, and an outer member formed with an internal gear engaged with the planetary gear. In the recessed portion, a protrusion is formed on one surface and not formed on the other surface.
Therefore, when the inner member rotates in a predetermined direction and the planetary gear is brought into contact with the other surface (the surface not formed with a protrusion) of the recessed portion, the planetary gear rotates in the recessed portion of the inner member. In this case, the planetary gear only causes a change of engagement with respect to the internal gear of the outer member, and therefore torque is not transmitted from the inner member to the outer member.
However, when the inner member rotates in a direction opposite to the predetermined direction and the planetary gear is brought into contact with one surface (the surface formed with a protrusion) of the recessed portion, the rotation of the planetary gear in the recessed portion of the inner member is locked by the protrusion. In this case, the planetary gear cannot cause the change of engagement with respect to the internal gear of the outer member, and therefore the torque is transmitted from the inner member to the outer member via the planetary gear.
Furthermore, since the one-way clutch described above does not cause the torque to be transmitted to the outer member when the inner member rotates in the predetermined direction, the feeding roller does not rotate. Thus, the feeding roller does not rotate in either one case of the forward rotation or the reverse rotation of the transporting roller. Therefore, it is necessary for the driving mechanism to cause the feeding roller to rotate in one direction whenever the transporting roller rotates in the forward direction of the reverse direction.
FIGS. 11A and 11B show schematic views of a driving mechanism which adopts a plurality of one-way clutches so as to enable the feeding roller to rotate in one direction whenever the transporting roller rotates in the forward direction of the reverse direction. In the driving mechanism, one-way clutches 174 and 176 are respectively provided on both sides of a center gear 172 which is engaged with a gear 170 receiving a driving force from the transporting roller. Hereinafter, the driving mechanism will be described.
The one-way clutch 174 disposed on one side of the center gear 172 includes an outer member 174a and an inner member 174b. The one-way clutch 174 is configured so as to transmit torque when rotating in a predetermined direction (a counter-clockwise direction in FIGS. 11A and 11B). In addition, the one-way clutch 176 disposed on the other side of the center gear 172 includes an outer member 176a and an inner member 176b. The one-way clutch 176 is configured so as to transmit torque when rotating in a direction opposite to the predetermined direction (a clockwise direction in FIGS. 11A and 11B).
The outer member 174a of the one-way clutch 174 is engaged with a gear 178, and the gear 178 is engaged with a gear 180. The gear 180 is engaged with a driving gear 182 for driving a feeding roller and is coaxially provided with a gear 184. Furthermore, the outer member 176a of the one-way clutch 176 is engaged with a gear 186, and the gear 186 is engaged with a gear 188. The gear 188 is engaged with the gear 184. In addition, the inner members 174b and 176b are configured so as to rotate together with the center gear 172 in a rotation direction of the center gear.
As shown in FIG. 11A, the center gear 172 rotates in a reverse direction, namely a counter-clockwise direction, when the gear 170 rotates in a forward direction, namely a clockwise direction. Corresponding to this rotation, the inner members 174b and 176b rotate in a counter-clockwise direction, as well. Thereby, the one-way clutch 174 is in a torque-transmittable state, and therefore the outer member 174a and the inner member 174b integrally rotate in a counter-clockwise direction. In addition, since the one-way clutch 176 is in a non-torque-transmittable state, the outer member 176a can rotate relatively to the inner member 176b. 
When the outer member 174a rotates in a counter-clockwise direction, the gear 178 rotates in a clockwise direction. Thus, the gear 178 causes the gear 180 to rotate in a counter-clockwise direction. The gear 180 causes the driving gear 182 to rotate in a clockwise direction. Furthermore, when the gear 180 rotates in a counter-clockwise direction, the coaxial gear 184 rotates in a counter-clockwise direction, as well. Thus, the gear 184 causes the gear 188 to rotate in a clockwise direction. The gear 188 causes the gear 186 to rotate in a counter-clockwise direction, and the gear 186 causes the outer member 176a to idly rotate in a clockwise direction.
On the other hand, the center gear 172 rotates in a forward direction, namely a clockwise direction, when the gear 170 rotates in a reverse direction, namely a counter-clockwise direction, as shown in FIG. 11B. Corresponding to this rotation, the inner members 174b and 176b rotate in a clockwise direction, as well. Thereby, the one-way clutch 176 is in a torque transmission state, and therefore the outer member 176a and the inner member 176b integrally rotate in a clockwise direction. In addition, since the one-way clutch 174 is in a non-torque-transmission state, the outer member 174a can rotate relatively to the inner member 174b. 
When the outer member 176a rotates in a clockwise direction, the gear 186 rotates in a counter-clockwise direction. Thus, the gear 186 causes the gear 188 to rotate in a clockwise direction. The gear 188 causes the gear 184 to rotate in a clock-clockwise direction. Furthermore, when the gear 184 rotates in a counter-clockwise direction, the coaxial gear 180 rotates in a counter-clockwise direction, as well. Therefore, the gear 180 causes the driving gear 182 to rotate in a clockwise direction. In other words, the feeding roller in the driving mechanism is driven rotatably in one direction regardless of the rotation direction of the transporting roller. In addition, when the gear 180 rotates in a counter-clockwise direction, the gear 180 causes the gear 178 to rotate in a clockwise direction. The gear 178 causes the outer member 176a to idly rotate in a counter-clockwise direction.
Meanwhile, corresponding to the rotation direction of the center gear 172, either one of the one-way clutch 174 or the one-way clutch 176 in the driving mechanism is in a non-torque-transmittable state. Therefore, the one-way clutch 174 or the one-way clutch 176 idly rotate with respect to the center gear 172 by the gears 178 and 186 respectively engaged therewith. At this time, only the dead load of the one-way clutch acts on each of the one-way clutches 174 and 176 rotating idly.
Therefore, a force which causes the idle rotation of the one-way clutch 174 or 176 to be braked does not act in the idle-rotation direction of the one-way clutch 174 or 176. Thus, when a tooth of the gear 178 is brought into contact with a tooth of the one-way clutch 174 so as to cause the one-way clutch 174 to rotate idly, the tooth of the one-way clutch 174 is swiftly displaced in an idle-rotation direction.
As a result, before the next tooth of the gear 178 is displaced to the position where the next tooth is to be engaged with the one-way clutch 174, a tooth of the one-way clutch 174 which is adjacent to the displaced tooth of the one-way clutch 174 is displaced to the engagement position. Therefore, the adjacent tooth of the one-way clutch 174 is brought to collide with the tooth of the gear 178 which has caused the tooth of the one-way clutch 174 to be displaced. In other words, the idle rotation of the one-way clutch 174 is performed prior to the rotation of the gear 178, and therefore the engagement between the gear 178 and the one-way clutch 174 is not carried out smoothly.
In addition, when the tooth of the one-way clutch 174 collides with the tooth of the gear 178, collision noise is generated between them. Therefore, the one-way clutch 174 is not smoothly engaged with the gear 178 during the idle rotation of the one-way clutch 174, and thus the collision noise is continuously generated in the teeth of the gears. Similarly, the collision noise is continuously generated in the one-way clutch 176 when the one-way clutch 176 is idly rotated by the gear 186. Thus, the driving mechanism has a problem in that operation noise thereof is loud in a driving state.